Igniter plug

ABSTRACT

An igniter plug for a turbine engine which has increased life and improved ignition capabilities. The igniter plug is characterized by an angled end portion which extends into a combustion chamber of a turbine engine. The angled end of the plug fits the contour of the combustion chamber, to permit freer flow of gases past the plug tip while at the same time allowing maximum projection and exposure of the spark into the combustible mixture.

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United States Patent 11 1 Meyer [451 Apr. 15, 1975 1 IGNITER PLUG [75]Inventor: Helmut P. Meyer, Sidney, NY.

[73] Assignee: The Bendix Corporation, Southfield,

Mich.

[22] Filed: Jan. 28, 1974 [21] Appl. No.: 437,258

[52] US. Cl. 313/118; 313/137; 313/141; 313/143 [51] Int. Cl. H011 13/20[58] Field of Search 313/141-145, 313/118,137; 123/169 P, 169 PA, 169 E2[56] References Cited UNITED STATES PATENTS 1,037,307 9/1912 Pierrel313/143 X 1,192,003 7/1916 Schmidt 313/141 1,452,054 4/1923 Propst313/141 X 1,540,137 6/1925 Lautenschlager 313/141 X 2,693,082 11/1954Arthur 313/143 X 3,745,400 7/1973 Meyer 1. 313/144 PrimaryExaminerAlfred L. Brody Attorney, Agent, or FirmRaymond J. Eifler [57]ABSTRACT An igniter plug for a turbine engine which has increased lifeand improved ignition capabilities. The igniter plug is characterized byan angled end portion which extends into a combustion chamber of aturbine engine. The angled end of the plug fits the contour of thecombustion chamber, to permit freer flow of gases past the plug tipwhile at the same time allowing maximum projection and exposure of thespark into the combustible mixture.

3 Claims, 1 Drawing Figure IGNITER PLU;

BACKGROUND OF THE INVENTION This invention relates to a spark dischargedevice for igniting combustible materials and more particularly to animproved igniter plug for igniting fuel in a turbine or jet engine. Thisinvention is most particularly related to the novel configuration of theelectrical discharge end of the igniter plug that ignites combustiblegases.

lgniter plugs generally comprise a metal shell or body that has a flangeor other mounting means for mounting the igniter plug in a ttlrbineengine. the shell constituting one electrode of the igniter plug. Acentral electrode passes through the shell and is supported by aninsulator which surrounds the central electrode and which is fitted intoan opening in the metal shell. A copper packing ring or bushing is thenprovided between the insulator and the shell in order to seal theopening in the body. through which the insulator extends. against escapeof gases. One example of a prior art igniter plug may he found in U.S.Pat. No. 3.745.400 entitled lgniter Plug issued July l0. 1973 to H. P.Meyer. hereby expressly incorporated by reference.

The igniter plug is mounted so that the discharge end that supplies theelectric discharge to ignite the fuel extends into the combustionchamber of the engine. Because of the extremely high temperaturesencountered during combustion of the gases and the impingement of therapidly flowing gases on the spark plug. the discharge end of the sparkplug wears away until the spark plug is no longer capable of ignitingfuel in the engine.

SUMMARY OF THE INVENTION This invention provides an improved igniterplug for turbine or jet engines that has an increased life span and ismore effective in igniting fuel in the engine.

The invention is an igniter plug characterized by an angled surface atthe discharge end of the igniter plug.

In one embodiment of the invention. the igniter plug comprises an innerelongated electrode (30) having a front portion (32). a rear portion anda central axis. a forward elongated insulator (80) disposed around theforward portion of said electrode (30): an intermediate elongatedinsulator (40) disposed around at least a rear portion of the electrode(30). the intermediate insulator (40) having a front portion and a rearportion; an outer elongated metal shell disposed around the electrodeand electrically isolated therefrom by the forward (80) and intermediate(40) insulators. metal shell (20) having a rear portion that has anopening therein and a front end portion (23) arranged to provide a sparkgap with the end of the front portion (32) of the electrode theimprovement wherein the front end of the spark plug terminates in anangled surface comprising: the front portion of the inner elongatedelectrode (30) which terminates in a first angled surface one end of theforward elongated insulator (80) which terminates in an angled surface(85) parallel to the first angled surface (35 and the forward end of thefront end portion of the metal shell (20) which terminates in an angledsurface (25) parallel to the first angled surface (35).

Accordingly. it is an object of this invention to provide an igniterplug that has an increased life span.

It is another object of this invention to provide an igniter plug thatprovides a more effective electrical discharge to ignite the fuel in aturbine or jet engine.

it is a further object of this invention to provide an igniter plughaving an angled surface at the electric arc discharge end of the plugto improve the performance of the plug.

The above and other objects and features of the invention will becomeapparent from the following detailed description taken in conjunctionwith the accompanying drawings and claims which form a part of thespecification. Further. the use of numerals in any portion ofthespecification is for the purpose of facilitating an understanding of theinvention and is not intended to limit the scope of the invention to thespecific embodiments referenced.

DETAILED DESCRIPTION OF THE DRAWING The single FlGURE illustrates anigniter plug incorporating the objects of this invention.

The igniter plug comprises an elongated central electrode 30; an outermetal shell 20 which forms the second electrode; a forward insulator anda rear insulator 40.

The central electrode 30 is generally comprised of an electricallyconducting material so that when an electric potential is applied acrossthe central electrode 30 and the outer shell electrode Zll. an arcdischarge may be formed between the tip 32 of the inner electrode 30 andthe surrounding portion 23 of the shell electrode 20. The end portion ofthe electrode 30 from which the spark discharge occurs is acylindrically shaped end portion 32 that is of a much larger diameterthan the rest of the electrode which contains therein one or morepassages 3| for the passage of gas to cool the tip of the electrode 30during operation. The end portion 32 of the electrode 30 terminates inan angled surface 35. makes an angle of about 30 with the central axisof the inner electrode 30. Coaxially disposed around the centralelectrode 30 is a ceramic insulator 40 which electrically isolates thecentral electrode 30 from the outer shell electrode 20. To prevent anygases from escaping through the rear end of the spark plug (not shown).the rear end of the spark plug is sealed so that no gases may escape.

A second forward ceramic insulator 80. having a shoulder 81. is alsopositioned within the shell 20 to prevent radial and axial movement ofthe control electrode 30 that might result in contact between thecontrol electrode 30 and the shell electrode 20. hence preventingelectrical short circuits. The insulator 80 has a rear portion and afront portion having an angled end surface that makes an angle of about30 with the central axis of the electrode 30. The angled end surface 85therefore provides an end surface having an inclination of about 30 tothe main axis of the insulator and parallel with the end surface 35 ofthe electrode 30.

The outer shell 20 includes a mounting flange (not shown] for mountingthe igniter plug to a turbine engine: intake and exhaust ports 21 and 22for allowing the entrance and exit of engine gases into the igniter plugto cool the electrode 30'. and a forward shell portion or cap 23 that iswelded to the shell 20. The front portion of the shell includes anangled surface 25 that is parallel to the angled surface 35 of the innerelectrode 30; and an opening that forms the discharge surface of theshell that together with the angled surface 35 of the control electrode30 forms the discharge gap which when energized ignites the fuel. Thiscap 23 also has an internal angled surface 26 which mates with theangled surface 86 of the forward insulator 80. When assembling theigniter plug. the last two pieces added to the assembly are the forwardceramic insulator 80 and then the shell cap 23 which is welded to shell20 to retain the forward insulator in a position that isolates thecentral electrode 30 from the outer electrode 23. The shell 23 and theinsulator 80 are now in 360 mated contact between surfaces 86 and 26.The cap 23 and insulator 80 are axially assembled with the same case assymmetrical parts. but provide an igniter with an inclined end surface.

The igniter plug shown in its operating position wherein it extendsthrough the outer wall 2 ofthe cornbustion chamber so that it isgenerally flush with the inner wall I of the combustion chamber of theengine. It is the inventor's belief that the angled or oblique endportion of the igniter plug which extends into the combustion chamberincreases the effectiveness of the igniter plug and increases its life.Preferably. the igniter plug is mounted so that the end surface 25 ofthe shell 20 is flush with the wall 2 of a combustion chamber.

While a preferred embodiment of the invention has been disclosed. itwill be apparent to those skilled in the art that changes may be made tothe invention as set forth in the appended claims and. in some cases.certain features of the invention may be used to advantage withoutcorresponding use of other features. Accordingly. it is intended thatthe illustrative and descriptive materials herein be used to illustratethe principles of the invention and not to limit the scope thereof.

Having described the invention. what is claimed is:

T. ln combination with a spark plug of the type having an innerelongated electrode having a front portion. a rear portion. and acentral axis; a forward elongated insulator disposed around the forwardportion of said electrode; an intermediate elongated insulator disposedaround at least the rear portion of said electrode; an outer elongatedmetal shell disposed around the electrode and electrically isolatedtherefrom by the forward and intermediate insulators. said metal shellhaving a front end portion arranged to provide a spark gap with the endof the front portion of said electrode. the improvement wherein thefront end of said spark plug terminates in an angled surface comprising:

the front portion of said inner elongated electrode which terminates ina first angled surface;

one end of the forward elongated insulator which terminates in an angledsurface parallel to said first angled surface; and

the forward end of the front end portion of said metal shell whichterminates in an angled surface parallel to said first angled surface.

2. The combination recited in claim 1 wherein the parallel angledsurfaces are about 30 from a plane that is perpendicular to the centralaxis of said inner elongated electrode.

3. A spark plug comprising an inner elongated electrode having acylindrically shaped front portion and a central axis; an elongatedinsulator means disposed around at least a portion of the electrode: anouter elongated metal shell disposed around the electrode and insulatormeans and electrically isolated from the electrode by said insulatormeans. said metal shell having an annular front portion arranged aroundthe inner electrode to provide an annular spark gap with the end of thefront portion of said electrode. and wherein the front end of said metalshell is equidistant at all adjacent points between the end of the innerelectrode and the end of said metal shell the front end of saidelongated electrode and the front end of said metal shell terminates inangled surfaces which are parallel to each other. with the front end ofsaid metal shell extending beyond the adjacent front end of said innerelectrode. l

1. In combination with a spark plug of the type having an innerelongated electrode having a front portion, a rear portion, and acentral axis; a forward elongated insulator disposed around the forwardportion of said electrode; an intermediate elongated insulator disposedaround at least the rear portion of said electrode; an outer elongatedmetal shell disposed around the electrode and electrically isolatedtherefrom by the forward and intermediate insulators, said metal shellhaving a front end portion arranged to provide a spark gap with the endof the front portion of said electrode, the improvement wherein thefront end of said spark plug terminates in an angled surface comprising:the front portion of said inner elongated electrode which terminates ina first angled surface; one end of the forward elongated insulator whichterminates in an angled surface parallel to said first angled surface;and the forward end of the front end portion of said metal shell whichterminates in an angled surface parallel to said first angled surface.2. The combination recited in claim 1 wherein the parallel angledsurfaces are about 30* from a plane that is perpendicular to the centralaxis of said inner elongated electrode.
 3. A spark plug comprising aninner elongated electrode having a cylindrically shaped front portionand a central axis; an elongated insulator means disposed around atleast a portion of the electrode; an outer elongated metal shelldisposed around the electrode and insulator means and electricallyisolated from the electrode by said insulator means, said metal shellhaving an annular front portion arranged around the inner electrode toprovide an annular spark gap with the end of the front portion of saidelectrode, and wherein the front end of said metal shell is equidistantat all adjacent points between the end of the inner electrode and theend of said metal shell the front end of said elongated electrode andthe front end of said metal shell terminates in angled surfaces whichare parallel to each other, with the front end of said metal shellextending beyond the adjacent front end of said inner electrode.